UNIT12. When ...? and How long ...? For and since

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A. Compare When ...? (+ past simple) and How long ...? (+ present perfect): A: When did it start raining? B: It started raining an hour ago/at 1 o'clock. A: How long has it been raining? B: It's been raining for an hour/since 1 o'clock. A: When did Joe and Carol first meet? B: They first met a long time ago/when they were at school. A: How long have Joe and Carol known each other? B: They've known each other for a long time. /since they were at school. B. We use both for and since to say how long something has been happening. We use for when we say a period of time (two hours, six weeks etc.): * I've been waiting for two hours. for two hours two hours ago -> now two hours/a week/20 minutes/50 years/five days/a long time/six months/ages * Sally's been working here for six months. (not 'since six months') * I haven't seen Tom for three days. (not 'since three days')

We use since when we say the start of a period (8 o'clock, Monday, 1985 etc.): * I've been waiting since 8 o'clock. since 8 o'clock 8 o'clock -> now since 8 o'clock/1977/Monday/Christmas/12 May/lunchtime/April/they were at school * Sally's been working here since April. (= from April until now) * I haven't seen Tom since Monday. (= from Monday until now) It is possible to leave out for (but not usually in negative sentences): * They've been married (for) ten years. (with or without for) * They haven't had a holiday for ten years. (you must use for) We do not use for + all ... (all day/all my life etc.): * I've lived here all my life. (not 'for all my life') C. We say 'It's (a long time/two years etc.) since something happened': * It's two years since I last saw Joe. (= I haven't seen Joe for two years/the last time I saw Joe was two years ago) * It's ages since we went to the cinema. (= We haven't been to the cinema for ages) The question is How long is it since ...? * How long is it since you last saw Joe? (= When did you last see Joe?) * How long is it since Mrs Hill died? (= When did Mrs Hill die?)